The present invention relates to electrical-to-optical converters, and more particularly to a self-contained, self-calibrating circuit apparatus for converting an electrical signal to an optical signal and for transmitting the optical signal through an optic fiber.
Circuits to convert analog electrical signals to analog optical signals are generally known. For example, U.S. Pat. No. 4,281,253 discloses a bidirectional optical fiber assembly that uses a dual function diode which functions both as a light emitter and as a detector of optical signals. U.S. Pat. No. 4,468,765 discloses optical fiber links for use in electronic telephone exchanges and employs an optical transmitter which consists of an LED coupled into an optical fiber. U.S. Pat. No. 4,481,676 is for a transmitter-receiver system for variable-rate digital data transmission via optical-fiber links which eliminates the effect of overoscillations and extends the input dynamic range. U.S. Pat. No. 4,547,774 discloses an optical communication system for drill hole logging having an armored cable containing optical fibers. A neodymium laser in a cable reel radiates light onto one of the fibers, a modulator downhole returns it to the surface, and a detector in the reel demodulates the data signal from the returning light. U.S. Pat. No. 4,644,587 discloses an optical data communication system with an optical star repeater which converts an optical signal into an electrical signal, amplifies the electric signal, reconverts the amplified electric signal into an optical signal, and then distributes the signal through fiber optic cables. U.S. Pat. No. 4,875,215 discloses a modular, optical fiber based laser communication system consisting of a sectionally doped optical fiber. U.S. Pat. No. 4,911,519 discloses a packaging technique for optical transmitters/receivers which significantly decreases the parasitic capacitance associated with conventional dual-in-line connections. U.S. Pat. No. 4,916,689 is directed to providing a fiber optic multiplexing controller for interfacing between one or more signal sending units, such as a control computer, and a number of devices to be controlled, such as relays or remote control circuit breakers. Each transmit section includes an optical transmission means for converting an electrical signal to an optical signal and for transmitting the optical signal through a fiber optic cable.
In certain circumstances, an operating environment is so harsh that it is very difficult to obtain accurate and reliable data from a physical event by conventional methods. For example, the detonation of a nuclear device generates such tremendous electromagnetic force that conventional electrical or optical devices are destroyed or severely damaged by the electromagnetic force before any useful data can be obtained.
Thus, it would be desirable to provide a device that could accurately and reliably obtain analog data from a physical event even under harsh operating conditions. The present invention does so with a signal conditioning device that provides a method for transmitting self-calibrated analog signals over optical fibers, thus eliminating the electromagnetically-induced noise normally associated with hard wire coupled data transmission systems.